jkress,
We also see this same symptoms.
avast version 8.0.1603.
We’ve had this issues since I can remember. We just started using Avast last summer.
Ive just put up with it until now, but I have another department that had to go to AVG or something else because Avast was breaking their Mapped drives to MS servers. We are a Novell shop so, no Domain here.

To add to your description. Even though you get the error while going thru My Computer, you can completely browse the mapped drive using command prompt. You just cannot see any folders or files. I just mapped drive Y to a server, changed to drive y. created a folder called software, copied files to this folder. All from a windows 7 workstation.
From the Server, I can see everything.
From my Win7 computer mapping to that share, all I can see are empty directories.
I can’t even see the directories, but I know they are there as I can change into one, and I get an error that the path doesn’t exist if I typo the directory name.

Same story, if I uninstall Avast, I can see everything. When I install avast. everything is hidden again.

I just mapped a drive from my XP computer and I can see files.
It was on version 8.0.1490.
I run the update to 8.0.1603.
restarted, mapped drive (I always map via cmd prompt)
I can see files.

Anyone have a fix or a link on how to fix this?